This invention relates to an output control apparatus, for a vehicle, which rapidly reduces driving torque of an engine according to an amount of slippage of the driving wheels, hereinafter referred to as slip amount, occurring during acceleration or the like, of the vehicle, thereby ensuring safe running of the vehicle.
When the road surface condition abruptly changes during operation of a vehicle, or when a vehicle is operating on a slippery road with a low frictional coefficient such as a road covered with snow or a frozen road, the driving wheels may often skid.
In such a case, it is difficult for even a skilled driver to adjust the amount of pressure applied to an acceleration pedal and delicately control the engine output to prevent the driving wheels from skidding.
To prevent this, an output control apparatus can be used which detects a skidding condition of the driving wheels. When skidding of the driving wheels occurs, the output control apparatus forcibly reduces the output of the engine independent of the amount of pressure applied to the accelerator pedal by the driver. Further, an apparatus is proposed which allows a selectable operating mode using the output control apparatus, or a normal operating mode, in which the output of the engine is controlled according to the amount of pressure applied to the accelerator pedal, selectable by the driver as necessary.
As an output control method according to this concept, an apparatus is known which detects, for example, a rotation speed of the driving wheels and a rotation speed of the driven wheels. It regards a difference in the rotation speed between the driving and the driven wheels as a slip amount. It then sets a target driving torque according to the slip amount and the operating condition of the vehicle, and controls the throttle valve opening and ignition timing so that the driving torque of the engine is that of the target driving torque.
In a prior art output control apparatus of a type in which a target driving torque of the engine is calculated according to the traveling condition of the vehicle, and the target driving torque is corrected according to a slip amount of the driving wheels, since the target driving torque is set to a same value as that for straightforward traveling, even when the vehicle is turning, it has been defective in terms of the drive feeling in that the acceleration feeling of the vehicle is impaired when the vehicle completes the turning and turns into a straightforward traveling condition.
Since, a side force is applied to the vehicle during turning, a higher driving torque than that for straightforward traveling is required in order to turn the vehicle with the same travel feeling as in the straightforward traveling condition before turning. However, since, in the prior art output control apparatus for a vehicle, the target driving torque during turning of the vehicle is set to a value which is almost same as the target driving torque for straightforward traveling, and the driving torque is set to a relatively smaller value so that a correction amount to the target driving torque during the slipping of the driving wheels does not become too large a value, the driving torque of the vehicle does not increase. This tends to deteriorate the acceleration feeling of the vehicle, when the vehicle turns from the completion of turning into a straightforward traveling condition.